This invention relates to electromagnetic wave antennas and more particularly to a transmission line antenna.
A transmission line antenna is similar to the directly driven resonant radiator type of antenna, except that two capacitors are used as a matching network instead of directly feeding the antenna at an impedance tap as well as consisting of a variable section of shorted transmission line having a length less than a quarter wavelength of the operating frequency. The transmission line input impedance remains substantially inductive over the frequency range. The capacitors, moreover, are adapted not only to resonate the antenna to the desired frequency, but also act as an impedance divider to provide the required input impedance, for example, 50 ohms. Several sections of shorted transmission line when desirable can be placed parallel across the tuning capacitors. The parallel combination of transmission line antennas reduces the input inductive reactance to facilitate matching and results in a more omnidirectional radiation pattern.